The half-life of `""_(38)^(90)Sr` is 28 years. What is the disintegration rate of 15 mg of this isotope?

Explanation

`T_(1//2) = 28 "years" = 28 xx 365 xx 24 xx 60 xx 60 s = 8.83 xx 10^8 s`
`(dN)/(dt) = lambda N = (0.693)/(T_(1//2)) xx N = (0.693 xx 15 xx 6.023 xx 10^(23))/(8.83 xx 10^8 xx 90)`
`= 7.877 xx 10^(10) Bq = (7.877 xx 10^(10))/(3.7 xx 10^(10)) = 2.1289 Ci`.